Author
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Hanneman Jr, Robert |
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JACKSON, SCOTT - UNIV OF WISCONSIN |
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Submitted to: Biotechnology Risk Assessment Symposium
Publication Type: Proceedings Publication Acceptance Date: 4/8/1996 Publication Date: N/A Citation: N/A Interpretive Summary: Foreign genes are being introduced into potato varieties to improve their pest resistance or quality. It is very likely that transgenic potato varieties will be grown in countries where natural wild potato species are endemic. Can these foreign genes be incorporated into natural populations? To answer these questions, crossability studies were undertaken to see if seed could be produced in crosses between all available wild and cultivated species and common varieties. Species were checked for their ability to produce pollen having the same chromosome number as their parents (2n gametes) and thus be able to cross to a wider array of species. Styles were checked to determine the degree of pollen tube growth in all crosses to assess barriers to hybridization. Seed set was determined. This crossability information is important to U.S. and foreign regulatory agencies to help them set policy with regard to the use of transgenics where endemic natural species exist, particularly if they wish to maintain genetically pure gene pools. The data also is of interest to breeders and geneticist who may wish to make crosses between wild species and common cultivars. This information is particularly beneficial to the countries of Central and South America where these species grow wild and to companies wishing to introduce transgenic potatoes into their agriculture. Technical Abstract: Crossability studies between wild tuber-bearing and closely related non-tuber-bearing Solanum species and cultivated tetraploid potato cultivars are being used to determine whether foreign genes can be transferred from transgenic cultivated potatoes to wild potato species populations. During the summer of 1994, 3969 pollinations were made using 96 wild species and subspecies [303 accessions (PI's)] as males to seven different cultivars, which resulted in successful crosses with 24 species. Seed set ranged from <1 to 78 seeds per fruit. The frequency of 2n pollen was determined for 315 accessions (100 species and subspecies) and ranged from 0-43 percent. The presence of 2n pollen permits successful crosses between 4x(4EBN) cultivars, as females, and both diploid and tetraploid 2EBN species. For a cross to succeed, the Endosperm Balance Number (EBN) hypothesis requires that the EBN's of the parents match directly, or through chromosome doubling or 2n gametes. Pollen tube growth for many of the crosses was evaluated to determine the presence or absence of stylar barriers, particularly when there was failure to set seed. During the spring of 1995, 115 species (233 PI's) were grown in the greenhouse to use as females in crosses to cultivars to test for 2n egg production. |
